Willie Walsh has dismissed the prospect of work on a third runway at Heathrow moving forward speedily and denounced the proposed cost as “bullshit”.

Walsh, chief executive of British Airways and Iberia parent IAG, also accused the government of “a missed opportunity” in not legislating to control the costs of the runway.

He said: “The £14 billion price Heathrow is talking about is outrageous and unacceptable. It’s complete bullshit.”

Walsh told the Guild of Travel Management Companies (GTMC) conference in Ireland: “We will probably see a second runway at Gatwick before we see a third runway at Heathrow.”

He noted transport secretary Chris Grayling’s insistence that costs to passengers must not rise but said: “The government has missed an opportunity.”

Walsh said: “There is a strong economic argument to expand Heathrow, but not at any price.

“The original budget was £18 billion. The runway was going to cost just £180 million of that. Who needs an £800 million car park?

“If Heathrow could get away with £20 billion it would. They have never had to control their costs. The more they spend the more they make.”

Walsh insisted: “The runway could be built for less than £10 billion. It should not lead to any increase in passenger charges, but if that is not clear in legislation, Heathrow will make off like bandits again.”

He added: “Heathrow has made commitments on the environmental impact. They have got to meet them. People won’t accept [anything less]. There is a lot of work to be done.”